In a recording method by an ink jet printer, which is one typical method among a variety of color recording methods, recording is executed by generating ink droplets, and attaching the same to any of a variety of record-receiving materials (e.g., paper, film, and fabric, etc.). According to this method, a recording head is not brought into direct contact with the record-receiving material; therefore, generation of noise can be reduced thus achieving silent recording. In addition, due to having the features of a reduced size and an increased speed that can be readily achieved, prevalence in recent years has rapidly progressed, and great advancement hereafter is expected.
Aqueous inks containing a water soluble coloring matter dissolved in an aqueous medium have been used as conventional inks for fountain pens, felt pens etc., and inks for ink jet printing. Furthermore, to these aqueous inks is generally added a water soluble organic solvent in order to prevent pen tips or ink discharge nozzles from clogging with the ink. For these inks, demanded are abilities to generate a recorded image with satisfactory density, probability of avoiding occurrence of clogging at pen tips and nozzles, favorable drying characteristics on the record-receiving materials, suppression of bleeding, superior storage stability, and the like. Additionally, particularly high solubility in water, and high solubility in a water soluble organic solvent added to an ink are required for the water soluble coloring matter for use. Moreover, fastness such as water resistance, light resistance, gas resistance and moisture resistance has been required of the recorded image.
Of these, gas resistance means resistance to a phenomenon of causing discoloration of a printed image via an action of ozone gas or the like present in the air and having an oxidizing action on a coloring matter in the record-receiving material. In addition to the ozone gas, NOx, SOx, and the like are exemplified as the oxidizing gas having this type of action. However, among these oxidizing gases, ozone gas is considered to be the main causative substance that promotes the discoloration phenomenon of ink jet images. Therefore, particularly ozone gas resistance among resistance to gasses tends to attract the most importance. A material entity such as a porous white inorganic substance is often used in ink-receiving layers provided on the surface of photo image-quality exclusive ink jet paper in order to accelerate drying of the ink, and also to suppress bleeding of high quality images. Discoloration due to ozone gas is markedly found on such recording papers. Since this discoloration phenomenon resulting from oxidizing gas is characteristic in ink jet images, improvement of the ozone gas resistance is one of the most significant problems involved in ink jet printing methods.
Hence, in order to expand a field of application of printing methods in which an ink is used, further improvement of light resistance, ozone gas resistance, moisture resistance and water resistance is strongly demanded on ink compositions for use in ink jet printing and colored bodies obtained by coloring with the same.
Inks having a variety of hues are prepared from a variety of coloring matters, and black inks among them are important inks used in both mono color and full color images. Although many coloring matters have been proposed for use in black inks to date, products that meet market requirements have not yet been provided. Many of coloring matters proposed are azo coloring matters, and disazo coloring matters such as C. I. Food Black 2, etc., among these have problems of inferior color rendering properties, unfavorable water resistance and moisture resistance, as well as insufficient light resistance and gas resistance, and the like. With respect to polyazo coloring matters having an extended conjugated system, there are problems of generally low water solubility, a bronzing phenomenon likely to occur that provides a recorded image having metallic luster in part, as well as insufficient light resistance and gas resistance, and the like. In addition, in the case of azo-containing metal coloring matters proposed similarly in large numbers, some have favorable light resistance, but there exist problems of safety for living organisms, unfavorable environmental influences due to metal ions included, extremely inferior ozone gas resistance, and the like.
As the black coloring matter for ink jet having improved ozone gas resistance which has been the most significant problem in recent years, for example, compounds disclosed in Patent Documents 1 to 3 are exemplified. These compounds do not have ozone gas resistance that sufficiently meets market requirements, and the light resistance is also unsatisfactory. Furthermore, in regard to azo compounds having a benzimidazolopyrrolidone skeleton that is one characteristic feature of the trisazo compound of the present invention, descriptions are found in Patent Documents 4 to 7 and the like. Patent Documents 5 and 6 also disclose trisazo compounds, and these trisazo compounds have a symmetric structure provided by allowing both ends of a linking group including an azo structure to be further bound to two benzimidazolopyrrolidone skeletons via an azo structure; however, compounds similar to the asymmetric trisazo compound of the present invention are not disclosed. Additionally, Patent Documents 5 and 6 only disclose a small number of water soluble compounds and do not disclose any examples of use of black coloring matter as an ink jet ink. As an example of trisazo compounds for use in an ink jet ink having superior ozone gas resistance, a compound disclosed in Patent Document 8 is exemplified, which discloses that the compound can be used as a black coloring matter for use in a water soluble ink jet ink. Although these compounds have superior fastness, it tends to result in high chroma saturation for use in a black ink. Examples of black trisazo compounds for use in an ink jet ink having superior ozone gas resistance also include a compound disclosed in Patent Document 9; however, such compound has not sufficiently satisfied market requirements.
Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2003-183545
Patent Document 2: Japanese Unexamined Patent Application, Publication No. 2003-201412
Patent Document 3: Japanese Unexamined Patent Application (translation of PCT Application), Publication No. 2007-517082
Patent Document 4: International Publication No. 2004/050768
Patent Document 5: West German Patent No. 2004488
Patent Document 6: West German Patent No. 2023295
Patent Document 7: Japanese Unexamined Patent Application, Publication No. H05-134435
Patent Document 8: International Publication No. 2007/077931
Patent Document 9: International Publication No. 2005/054374
Patent Document 10: East German Patent No. 223149